I`ve never liked any amv`s, most are just bad or annoying :P
But like 2 weeks ago or something someone posted a link to an amv on another forum, I checked it out and it was great:
AMV - Lip Bomb // Multi-Anime by BestAmvEver3http://www.youtube.com/watch?v=rnOST2laSlk
The username fits him/her

Here a few amv's that I thought were done pretty well.
http://www.youtube.com/watch?v=L5SNeXI0sEY (one of my favorite amv's! It's got so many special effects!)
http://www.youtube.com/watch?v=YfqIOOKdx6k
http://www.youtube.com/watch?v=CZf7bUuVkGM
http://www.youtube.com/watch?v=kBfl-iXprYY